A common form of encapsulated semiconductor device comprises a boxlike body portion having a short mounting tab of plated copper or the like, the mounting tab being integrated with the encapsulated boxlike body portion so as to present a flat surface which is placed on and against the circuit board or the intermediate heat dissipator when the device is installed. Typically there is a hole formed in the mounting tab to receive a fastener or retainer such as a small threaded bolt which is used in combination with a threaded nut to secure the device to the circuit board. Other types of fasteners including screws and rivets can also be used.
The fastener devices mentioned above have at least two drawbacks: the first is the fact that the securing force is concentrated in the area of the mounting tab and this can cause the device to lift away from the mounting board in the area of the boxlike encapsulation structure. This greatly reduces heat transfer from the semiconductor to the circuit board or to the intermediate heat dissipation. The second disadvantage is the fact that such fasteners are cumbersome to install and/or remove.
The prior art shows various types of spring clip devices for securing semiconductors and the like in place. Deakin U.S. Pat. No. 2,917,286, for example, shows a spring clip comprising a central collar portion and outboard barbs which extend through two widely spaced holes in the circuit board or the like. Lackey U.S. Pat. No. 2,994,203 discloses a clip having a cylindrical case. Lindstrand U.S. Pat. No. 3,259,813 shows a clip for holding a device to a heat sink. Lavochkin U.S. Pat. No. 4,509,839 makes a similar disclosure of a clip for holding a transistor to a heat dissipator of the type having a flat central body portion and opposite upstanding wings or fins.